diff --git a/lib/source-code/source-code.js b/lib/source-code/source-code.js
index f3418e7e5b7..0b9c41ee6e1 100644
--- a/lib/source-code/source-code.js
+++ b/lib/source-code/source-code.js
@@ -935,7 +935,7 @@ class SourceCode extends TokenStore {
          * https://github.com/eslint/eslint/issues/16302
          */
         const configGlobals = Object.assign(
-            {},
+            Object.create(null), // https://github.com/eslint/eslint/issues/18363
             getGlobalsForEcmaVersion(languageOptions.ecmaVersion),
             languageOptions.sourceType === "commonjs" ? globals.commonjs : void 0,
             languageOptions.globals
diff --git a/tests/lib/linter/linter.js b/tests/lib/linter/linter.js
index 6e98b93f3a1..4f61a56bdc1 100644
--- a/tests/lib/linter/linter.js
+++ b/tests/lib/linter/linter.js
@@ -10310,6 +10310,38 @@ describe("Linter with FlatConfigArray", () => {
                         linter.verify(code, config);
                         assert(spy && spy.calledOnce);
                     });
+
+                    // https://github.com/eslint/eslint/issues/18363
+                    it("not throw when defining a global named __defineSetter__", () => {
+                        const code = "/*global __defineSetter__*/";
+                        let spy;
+
+                        const config = {
+                            plugins: {
+                                test: {
+                                    rules: {
+                                        checker: {
+                                            create(context) {
+                                                spy = sinon.spy(node => {
+                                                    const scope = context.sourceCode.getScope(node);
+                                                    const def = getVariable(scope, "__defineSetter__");
+
+                                                    assert.strictEqual(def.name, "__defineSetter__");
+                                                    assert.strictEqual(def.writeable, false);
+                                                });
+
+                                                return { Program: spy };
+                                            }
+                                        }
+                                    }
+                                }
+                            },
+                            rules: { "test/checker": "error" }
+                        };
+
+                        linter.verify(code, config);
+                        assert(spy && spy.calledOnce);
+                    });
                 });
 
                 describe("when evaluating code containing a /*global */ block with sloppy whitespace", () => {